1. Field of the Invention
The present invention relates to a coordinate input system for use in operating a cursor or window on the screen, and a method of controlling the coordinate input system.
2. Description of the Related Art
Heretofore, mouses and track balls have been generally used as pointing devices connected to computers. However, other types of pointing devices called pads, touch pads, track pads, etc. have also been employed recently. In practical use, those pads are built in portable personal computers or externally connected to desk top computers, and do not require to be moved in themselves unlike mouses. Thus, those pads have a feature that they can be operated without problems even in a limited space on a desk or the like.
To move a cursor (or also called a pointer) on the display screen of a computer by using such a pad, it is only required for a user to put a finger on a flat operating surface several centimeters square provided on the pad and then slide the finger while keeping contact with the operating surface. Similarly to a mouse, a pad includes a left button and a right button. In addition, as with the case of clicking the left button, various operations such as selecting and moving an object displayed on the screen, for example, an icon (i.e., a symbol pattern representing the function of an application program) or a window (i.e., any of multiple independent screens indicated on a display), can also be performed by softly tapping the operating surface with a finger. An action of carrying out those operations in such a manner is especially called "tap (action)" or "tapping".
By utilizing the above tap function, a pad makes it possible with one finger to perform not only the above-stated operation equivalent to clicking of the left button, but also other operations equivalent to double clicking of the left button (used to, e.g., start up an application program), in which the left button is clicked twice successively, and dragging. Here, the operation called dragging means an action to move an object displayed on the screen, such as an icon or window, from one position to another desired position on the screen.
The dragging can be realized with a pad by first putting a cursor upon an object displayed on the screen, such as an icon or window, then tapping the operating surface once, placing a finger on the operating surface immediately after the tapping, and sliding the finger on the operating surface from there while keeping contact therebetween (slide action), causing the cursor to move on the screen. Alternatively, as with the case of using a mouse, the dragging can also be realized by keeping the left button depressed by one finger with the cursor put on an object such as an icon, and simultaneously sliding another finger on the operating surface. When the finger is lifted off from the operating surface during the slide action of the finger on the operating surface, a drag mode is released and the object is moved to the position on the screen to which the cursor has moved.
Meanwhile, some pads are designed such that if a finger is moved a predetermined distance on the operating surface after coming into a drag mode, the drag mode can be held continuously even after the finger is lifted off from the operating surface. This function is called "drag lock" because the drag action is held in a locked state in spite of the finger being lifted off from the operating surface. Once brought into a drag lock state, even if the finger is lifted off from the operating surface during the slide action, it is possible to freely move the icon or window, upon which the cursor has been first put, on the screen under continuation of the drag mode by sliding the finger on the operating surface again.
Usually, an effective area on the operating surface of a pad is smaller than that on the display screen of a computer. Thus, a region on the operating surface of a pad where the user can move a finger has a different size in many cases from a region on the display screen of a computer where a cursor is movable. Assume now that dragging is to be performed by moving a cursor along a diagonal line from the lower left corner to the upper right corner of the display screen of a computer under environment devoid of the drag lock function. In this case, even when the user slides a finger along a diagonal line on the operating surface of the pad from the lower left corner to the upper right corner, the cursor on the screen is moved just to a position midway the diagonal line of the screen.
Accordingly, to complete the dragging on the display screen of the computer, the drag action must be repeated several times on the operating surface of the pad and this is very troublesome for users. On the contrary, in pads having the drag lock function, once the drag action is performed on the operating surface of the pad, it is only required thereafter to simply slide a finger on the operating surface of the pad in a like manner as required when the cursor is usually moved. Thus, a burden imposed on users can be alleviated to a substantial extent.
As described above, providing the drag lock function makes it possible to considerably simplify the pad operation necessary for the dragging. But it can be said that the drag lock state is fairly anomalous, considering from the standpoint of usual pad operation. Accordingly, users may be embarrassed because they can not understand what has happened, in the case that (1) the users are not familiar with the pad operation, or (2) the drag lock state has been brought unintentionally by false operation of the pad even when the users are skilled in the pad operation.